This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. For this pilot study we first want to assess the effect of food presentation, which has been used in IRB 326 (Section III.B), on glucose metabolism in normal subjects (Study I). Subjects will have 3 PET scans with 18F-fluorodeoxyglucose (FDG), which will be given on three different days (A, B or C) to assess the effects of behavioral intervention (visual, olfactory and perceptual presentation/exposure to food), neutral intervention (visual, olfactory and perceptual exposure to things such as pictures, toys, clothing items or questions that do not result in a strong emotional feeling or response) and baseline (no intervention) conditions. On the day of the behavioral or neutral intervention, the intervention will be started 15 minutes prior to FDG injection and will be continued for a total of 45 minutes. When this paradigm is feasible to assess the metabolic changes in control subjects, we will then compare the brain metabolic changes with obese subjects (Study #2). This information is essential because if we can't observe significant brain glucose metabolic changes using this paradigm we won't be able to do Study #2 and we will revise this study according to the preliminary data we have obtained. We will resubmit any proposed changes to the IRB for approval.